Unlike Old Faithful, which spews water like clockwork every hour-and-a-half, no one knows when Steamboat will erupt next.

In the past, it's gone as long as 50 years without a major event. In 1964, it erupted a record 29 times.Steamboat is one of more than 500 geysers at Yellowstone, which boasts the largest collection of hydrothermal features in the world. They're fueled by cold water seeping into a natural underground plumbing network, where heat from the park's volcano causes the periodic eruptions.